weak part vs soft spot

weak part and soft spot both are nouns.

Word	Noun	Adjective	Verb	Adverb
weak part	Yes	No	No	No
soft spot	Yes	No	No	No

As nouns, weak part and soft spot are synonyms defined as:

Other synonyms of weak part include weak spot.

weak part (noun)	soft spot (noun)
a place of especial vulnerability	a place of especial vulnerability
	any membranous gap between the bones of the cranium in an infant or fetus
	a sentimental affection